Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2012

Asset Retirement Obligations [Abstract]

ARO operating costs

	Three Months Ended March 31
in thousands	2012		2011
ARO Operating Costs
Accretion		$2,019		$2,172
Depreciation		1,864		1,541
Total		$3,883		$3,713

Reconciliations of ARO

	Three Months Ended March 31
in thousands	2012			2011
Asset Retirement Obligations
Balance at beginning of period		$153,979			$162,730
Liabilities incurred		0			0
Liabilities settled		(621	)		(2,332	)
Accretion expense		2,019			2,172
Revisions up, net		25			21
Balance at end of period		$155,402			$162,591